•then re-harden. Fig. 773 shews a handy emery wheel for trueing
up without preliminary softening. The shank A is fixed in the
slide-rest so as to let a vulcanite wheel E roll upon disc B fastened
to the catch plate, and the emery wheel c to just touch the centre
point, The knob D, loose on the spindle, is now taken hold
of to traverse wheel c, and the lathe mandrel is revolved, the
connecting band between spindles E and c being a long helical
JP. 157. Water-finishing Tool,—If a high and smooth
finish is to be given to iron or steel, a broad, sharp tool is used,
and plenty of water fed to its point while tooling. Quick speed
and large feed are also supplied, and the tool-points are shewn in
Fig. 774—A for a planer^ or shaper, and B for a lathe. The latter
form can be understood by remembering that the relative path
•of tool to work is that of a screw, while the tipping of the tool
at c permits its front to lie normally with the direction of travel,
P. 160. Face Lathe.—To give a clearer idea of this
machine, a general drawing is provided in Fig. 775. The
driving details have already been described for the break lathe,
and the slide-rest needs no further description. The only point
of difference lies in the bed, which, it will be seen, admits large
diameters having small axial width, It is thus a surfacing
J?. 260. Classification of Boring Machines.—A short
•classification will give a better understanding of the many types
of these machines. Thus, we may ha^e :
r, Boring in the lathe: with moving work,
2. Special boring machine of lathe pattern.
3. Horizontal boring machine: with fixed work.
4. Vertical boring machine.
5. Snout-boring machine, for blind holes.
Lathe boring has been described at p. 160; but as universal
tools are inadvisable, most machines being kept going with one
•class of work, it is better to construct a special machine (Class 2)
of c lathe-boring pattern, than to do much boring in the lathe